Module idle_gate 

Idle-gate registry — the generic armed-deadline primitive (WK.3).

A subsystem registers a handler and an armed deadline; when the deadline elapses the editor actor runs the handler and applies the Effects it returns. Which-key’s “hold a prefix for 300 ms” is the first consumer; “did you mean…” hints, idle-time prefetch and the inline-diagnostic gate are the obvious others.

Why a registry rather than a field

This is the third instance of a shape this codebase has twice decided is right. tick_callback’s module doc names the alternative as the smell it exists to kill:

rather than adding an Editor::drain_<x> method + an Option<Receiver> field per subsystem, a mode owns its channel and registers a closure that drains it.

A deadline field per subsystem is that same smell in the time domain, and Editor::inline_diag_deadline is the existing instance of it — a bespoke Option<Instant> on the editor plus a hand-written select! arm in the actor. One more subsystem wanting a delay would mean a second field and a second arm.

The inline-diagnostic gate is deliberately NOT migrated here (design §9): its arm decision runs inside publish_render_state, reading config, modal and cursor.line, and there is no cursor-moved typed event to subscribe to. Finishing that migration means publishing a CursorSettled event plus surgery on working code, and gating a discoverability feature behind an LSP refactor is backwards. This registry runs beside it.

Timing

The registry stores deadlines only; it owns no timer. The actor asks for earliest once per loop iteration and points its single pinned sleep there, then calls fire_elapsed when it wakes. That keeps every tokio concern in the actor and leaves this unit testable with a plain clock.

Lifecycle

register returns an RAII IdleGateHandle, mirroring TickCallbackRegistration: a mode aggregates the handle into its Guard, so a deactivated subsystem contributes no timer at all.

Structs

IdleGateHandle

RAII handle: arms and disarms one gate, and removes it on drop.

IdleGateRegistry

Registry of subsystem-contributed idle gates.

Type Aliases

IdleGateHandler

A gate’s body. Runs on the editor actor thread when the gate’s deadline elapses; returns the Effects the host applies.

IdleGateRegistryHandle

Typed handle for ServiceRegistry lookup. Per the Arc/TypeId rule, register and look up with the same T; this alias guarantees it.